Smaug: A 36" x 16" build.

[Gromit]

Re: Smaug: A 36" x 16" build - A dome design question

Martin,

I would imagine that the curve of my dome approximates a section of a sphere. I drew it by bending a metal ruler between two points until it looked like what I wanted. Designing it in google sketchup, I used the arc tool with a 2" bend. I am a geometry dummy and could not tell you the difference between an arc and an ellipse. No worries at all about the flat part of the dome being self-supporting. When you are constructing the dome, you will see that with just the slightest angle the bricks will hold each other in place

I think that the shape with the 9" soldier course that you have in mind will be good for bread baking--it will give you more volume in the lower part of the dome. If I were doing mine again, I would use the soldier course shape, but not the soldier brick layout even though I really like the look. I would use half-bricks for the first three courses, have them rise vertically, and lay the bricks on bond (if that is the proper bricklayers term of art.)

Good luck with your build. I look forward to following it. Post pics!

[Rodneyf]

Re: Smaug: A 36" x 16" build.

Looking good David! I am not far behind you with my oven curing happening this Friday. I hope my pizzas look as good as yours do and I am sure your tasted as good as they looked. Unlike you I don't yet have tools or even the right flour yet but I will take a trip to the local WFO pizza shop and see if he will let out some secrets as far as his flour supplier goes.

[daylight]

Re: Smaug: A 36" x 16" build.

Here is a picture of the elliptical curve for the dome - you can see how flat it would be for a large section. My more experienced helper, Les, took one look at it and said that he was concerned (code for "that will never work"). I will probably adopt your approach and go for a part-sphere. I have just drawn out the curve that will give me a dome height of just under 19" and it looks more practical - I am awaiting approval from Les!

Construction started todayso I will start a thread and document the build with photographs.

Martin.
[IMG]PhotoPlog - Dome and Floor[/IMG]

[Gromit]

Re: Smaug: A 36" x 16" build.

After about 10 firings, I decided to peel back the insulation and take a look at a crack that had developed during the curing fire. It looked worse from the outside than I expected, so I decided to buttress the dome with a few steel cables. One cable is anchored to the hearth slab and strung over the entry arch; it is kind of hard to see in the photos. I put the cables on the outside of the 1st blanket to protect them from the heat.

[Rodneyf]

Re: Smaug: A 36" x 16" build.

David, that is a crack for sure, what does it look like on the inside? Do you think you should fill the crack with a heat resistant filler as some others on the forum have done with success?

[Lars]

Re: Smaug: A 36" x 16" build.

Hey Rodney.
What is it, like the middle of the afternoon for you now? ( 1:00am here)

Lars.

[Rodneyf]

Re: Smaug: A 36" x 16" build.

It is a gorgeous sunny afternoon at about 22C and a slight westerly breeze.

[Dino_Pizza]

Re: Smaug: A 36" x 16" build.

Aw, David,
Why a crack? Do you know when it happened on your firing schedule? Without knowing the inside crack size, I would say it is about the same as mine. I don't think any heat escapes with the 3-4 layers of ceramic blanket I've got so I don't think you have anything to worry about, structurally or heat wise. You've been cooking in it so it's working fine and it's still a beautiful oven you've made, that's what's important to remember. If you decide to add any refmix to patch, it will make the gap a bit smaller but it will crack along there anyway. I filled my outside crack but I probably shouldn't have bothered. Cheers, Dino

[Gromit]

Re: Smaug: A 36" x 16" build.

Here is a fuzzy pic from the inside; it has opened up a little more since this pic was taken.

The crack happened right in between when the oven turned black and when it turned back white. So, I know exactly when it happened plus or minus 18 hours.

I was more worried about it from a structural standpoint than from a worry about heat escaping--not much gets through three overlapping layers of the blanket. I was afraid I might push my hoe/rake right through the soldier wall in an errant blow. I have not decided whether to seal it up from the inside with anything. Anybody have any links to suggested products? Any good reason to bother with it?

One interesting datapoint: When I peeled back the insulation, it was a day after firing. Midway up the dome, the IR gun gave an inside reading of 350F and the same point on the outside of the dome was 340F. I would love to know the outside temperature right at the two hour point of intense firing.

[dmun]

Re: Smaug: A 36" x 16" build.

Is it just me, or are we seeing more and worse cracks with the current vogue for full brick height soldiers?

[Gromit]

Re: Smaug: A 36" x 16" build.

Dmun,

I was aware of your warnings about soldiers before I started my build, but I decided to plow ahead anyhow because I liked the look and the shape of the soldier course. Maybe it is because it reminded me of the building in this picture which is 5 miles from my house.

NOW, seeing my big honking crack in my soldier course + a lot of other hairline cracks in the soldier, I would not use soldiers again. I would possibly still try to achieve that Astrodome shape with 1/2 bricks laid on bond (is that the correct term?) since is gives a bit more volume for a given height when compared to a hemisphere.

Please feel free to point people to the pictures of my great crack in your warnings about soldiers.

[Les]

Re: Smaug: A 36" x 16" build.

David, I'm not sure the soldier course is your enemy here. It might be, but I think your bigger problem is the stack bond. I didn't go the soldier route so I might be full of crap. Every pic of an oven I see with a major crack has always followed the line. I would cover it with a blanket and cook something - don't sweat it.

Les

[Gromit]

Re: Smaug: A 36" x 16" build.

I'm not sure the soldier course is your enemy here. It might be, but I think your bigger problem is the stack bond.

Les, I think that the soldiers and the stack bond achieve the exact same thing: long vertical sections of nothing but mortar that invite cracks.

I have a stack bond on top of a soldier, so I should be little surprised to find it cracked.